Cutting chain



June 20, 1944. N, u 2,351,738

CUTTING CHAIN Filed Aug. 22, 1941 I 2 Sheets-Sheet l June 20, 1944. A, N BLUM 2,351,7 38

CUTTING CHAIN Filed Aug. 22, 1941 2 Sheets-Sheet 2 Patented June 20, 1944 UNITED STATES PATENT OFFICE CUTTING CHAIN Arthur N. Blum, Philadelphia, Pa.

Application August 22, 1941, Serial No. 407,996

14 Claims.

The conventional cutting chain or a chain saw usually consists of cutting teeth and rakers, articularly interconnected. The chain runs at high speed and is guided by a suitably formed bar rail.

The cutting teeth, arranged on both sides of the chain, out two grooves into the wood and determine the width of the kerf, while the rakers, which are somewhat lower in height than the cutting teeth, break out the wood between the two out side grooves and transport it out of the kerf as sawdust.

As stated, the cutting chain travels at high speed; and in order to maintain a straight cut, the cutting teeth and the rakers must perform their respective functions symmetrically with respect to the median plane of the out. At the high speed with which the individual teeth attack the wood, even a slight unbalancing will cause a decided cutting out of 1inecurved instead of straight. This tends to pinch the guide rail in which the chain travels in the kerf, and

overheats and burns the rail, due to friction. Such unbalancing might be caused, for example, by 'an eccentric pressure on the machine while in the cut, or by the relative direction of the fibres v of the wood with respect to the plane of the cut,

or by an unsymmetrical disposition of the weight of the machine, with respect to the cutting plane.

The principal object of my invention is to compensate for such unbalancing effects by making the two parallel sets of outside cutting teeth, or the takers within, or both cutters and rakers asymmetrical in an additive sense with respect to the median plane which includes the normal center line of the chain, so that the ununiform tooth action at opposite sides of the plane will compensate for the unbalancing factor by tending to make the saw cut out of line in the opposite direction. Such effect may be obtained, for example, by making the two sets of teeth of uneven height, or in other ways as hereinafter described.

A further object of my invention is to make it possible to use the chain saws with a templet, as in framing, for example, and as set forth in my United States Patent No. 2,296,240. In cutting a beam on a bias, it is evident that one row of the outside cutting teeth will cut the fibres before the other row on the opposite side of the 'kerf. The resulting unequal cutting resistance might tend to curve the keri either against the templet, in which case the saw will Jam, or away from the templetI in which case it will cease to tollow it. By making the two opposite teeth of unequal height, or otherwise asymmetrical, as proposed by my invention, such cutting-out tendencies can be counteracted.

A still further object of the invention is to provide the guiding tails of the teeth, which engage with the guide rail, with curved or hooked contours, with the object, first, of scraping clean the groove in the guide rail from sawdust, and, second, to better transport and distribute the lubricating oil along the groove.

Another object of the invention is to provide the cutting chain with guiding tails having a slanting front, with the object when running at high speed and striking the sawdust accumulating in the groove, of keeping the chain steadily pressed against one side of its guide groove.

In the attached drawings:

Fig. 1 is a side view of a section of cutting chain made in accordance with the invention:

Fig. 2 is a cutting edge view of the chain shown in Fig. 1;

Fig. 3 is a back edge view of the chain;

view of one of the sets of the cutting teeth;

5 is an enlarged section on the line 5--5,

Fig. 6 is a cutting edge view of a modified form of cutting chain within the scope of the invention;

Fig. 7 is a view corresponding to that of Fig. 4, but illustrating another modification;

Fig. 8 is a diagrammatic view of the cutting edge of a chain illustrating still another modification;

Fig. 9 is a view in perspective of a novel device for setting the cutting teeth and illustrates its method of use;

Fig. 10 is a view showing a detail of one of the elements of the device; and

Fig. 11 is a view illustrating a desirable treatment of the raker teeth to improve the raker effect.

The typical cutting chain illustrated in Figs. 1 to 5 of the drawings comprises articulated chain links provided with cutting teeth I arranged in pairs with the teeth Ia and lb of each pair at opposite sides, respectively, of the median plane X, X of the chain. Each of the pairs of the cutting teeth is followed in succession by a single centrally arranged raker tooth 2, a set 3 of raker teeth of which the individual teeth 3a and 3b are, respectively, at opposite sides of the median 1 plane of the chain, and a second centrally arranged raker tooth 4. This grouping is repeated throughout the length of the chain.

The tops 5 of all of the teeth are uniformly inclined rearwardly toward the axis of the chain, so that the height of the teeth may be: reduced by cutting the teeth back from their leading faces 6. Geometrically expressed, it can be stated that the upper edges of the tops of all cutting teeth lie in parallel planes, shown in projection at P-1, in Fig. 1, which are tangential to imaginary cylinders, C-l, coaxial with the proximate axis of articulation O| of the chain links of such imaginary coaxial cylinders being of the same diameter. The upper edges of all raker teeth also lie in parallel planes P-TI, which, while parallel to the planes first named, are tangential to imaginary cylinders respectively coaxial with the proximate centers of articulation -2. All axes of articulation O-l, 0-2 intersect at right angles the median plane X-X of the chain and lie in a plane H-H which also intersects and is normal to the median plane.

But the imaginary cylinders C2 of the raker teeth which are equal among themselves are of smaller diameter than the coaxial cylinders C-l orthe cutting teeth. This is in accordance with the well known general rule that the raker teeth must not exceed the cutting teeth in height in order that the teeth may accomplish their respective functions and afford eifective cutting. The teeth may be sharpened by grinding the faces 6 as described in my United States Patent No. 2,318,456, and sharpening in this manner has the eil'ect of reducing the height of the teeth.

The fact that the upper edges of all the cutting and raker teeth are .located in planes which are parallel to each other aids materially in the mechanical precision-sharpening of the teeth because equal amounts removed from the fronts of the teeth effect an equal reduction of their heights whereby the originally required difierence in height between the cutting and raker teeth points is automatically maintained. When the faces of any of the pairs of cutting teeth I, or raker teeth 3, are sharpened in a common plane at right angles to the median plane of the chain, the respective teeth on the opposite sides of that plane will be of the same height, assuming, of course, that the inclinations of the backs of the two teeth are the same. By sharpening the two teeth at a front angle departing from 90, however, either tooth, at will, can be made higher or lower than the other by a specified amount.

Referring to Fig. 4, for example, it will be apparent that if the sharpening occurs in a plane Y, Y, at right angles to the median plane X, X of the chain, the height of the two teeth la and lb will be reduced by an equal amount; but if the sharpening occurs on a plane Z, Z at an angle a, less than 90, to the said median plane, the cutting edge of the tooth la. will not only lead the cutting edge of the tooth lb in the direction of chain movement, but by reason of the inclined backs of the teeth, the height of the tooth lb will be reduced to an extent greater than the reduction occurring in the tooth la. Thus. the height of the tooth lb will be less than the height of the tooth la by an amount h, see Fig. 5, which will depend upon the acuteness of the angle a and the degree of inclination of the backs 5 of the teeth. A similar effect will be obtained in the sets 3 of raker teeth if sharpened as described above, so that the raker tooth at one side of the median plane will be higher than the raker tooth at the opposite side. However,

due to the fact that for eflicient cutting the cutting teeth should be higher than the raker teeth, the reduction of height it between the cutting teeth la and lb leaves the lower teeth still higher than any of the raker teeth. as clearly shown in Figs. 1 and 5.

The effect obtained by the aforedescribed un uniform tooth formation is that the teeth on one side of the median plane 01' the cut will cut and dig deeper into the wood than the teeth on the other side; and by the consequent uneven reaction to effect the direction of the cut, the tendency being for the keri to follow the side having the teeth of greater height. It is to be noted further that the wood is also attacked by the higher teeth on the one side in advance of the teeth on the other side of the median plane. This also will effect the direction of the cut and will have a similar action as that described above. It will be apparent that the invention provides a method for selectively and predeterminably affecting the plane of the cut.

'In cutting chains in which the cutting teeth, or the rakers, or both, are not disposed in pairs on opposite sides of the chain, but are individually staggered, as in Figs. 6 and 8, for example, the required unequal heights may be imparted individually, but otherwise the method is substantially the same, and is due to the additive effect of the asymmetrical co-location of the teeth points on both sides of the median plane, or an unequal attack of the corresponding points of teeth of the same kind on opposite sides of the median plane. 'But again, these asymmetrical differences are limited by the requirement that cutting teeth must not be lower than the raker teeth.

The same efiect may be obtained when the single rakers are sharpened at an angle a, see Fig. 2. In this case, the edge I of the tooth, which is offset laterally from the median plane X, X, will lead the opposite edge 8--which lies on the opposite side of the plane-and will attack the wood first. Obviously, if the'rakers are sharpened at an angle a, the efiect will be reversed. Like effects may be achieved by sharpening some teeth in one sense and some in the opposite, provided that there is an additive resultant diiference in the two opposite angles, re sulting in a tendency of the chain to cut in a predetermined plane.

As indicated in Figs. 4, 5, 6 and 8, the width of the kerf K cut by the chain depends on the sum of the distances K1 and K: of the points of the cutting teeth from the median plane X-X of the chain. For the purpose of the present in;- vention, it maybe varied by imparting to these points an asymmetrical set. It will be seen from Fig. 5 that an asymmetrical set of the two opposite cutting points will result in a different height of these two points above the plane H-H which height difference may be varied. In Fig. 5, hi is greater than 71.2 and the difierence, '11 minus ha, taken additively will determine the corrective force which is to counteract the tendency of the cutting chain to cut in a curved kerf.

Still another method of accomplishing, structurally, the object of my invention is to give a set to all or some of the cutting teeth on one side of the median plane which'difiers from the set of the cutting teeth on the opposite side, see Fig. 7. Instead of giving the teeth a different clearance set, as shown in this figure, the dinerence in set may extend only to the tip set hereinafter described.

With teeth'of the type shown in Fig. 8 which have teeth tops similar to the ones shown in Figs. 1 and 5 but which have also the teeth fronts 6 beveled and sharpened, a corresponding effectv of the cut-scoring teeth at opposite sides respectively of said plane will also contribute to the desired effect. In each instance, there is, while cutting, a tendency for the chain to be urged to one side of the kerf more than to the other, thereby to compensate for any undesirable aberrating cutting tendency of the chain.

With reference to Figs. 1 and 5, it will be noted that certain links of the chain are formed to provide at the back of the latter a series of tails 9, these tails functioning to guide the chain in the guide rail. The rail ID, as shown in Fig. 5, may be provided with a longitudinal groove II for reception of the tail 9. In accordance with my invention, I have formed the leading edges I 2 of the tails 9 with a curved or hooked contour which tends to clear the groove i I of accumulated sawdust by the so created spur. Also, in accordance with the invention, I form the leading faces I! of the tails 9 in substantially parallel planes at an angle to the longitudinal line of the chain and of the groove II in the guide rail I0. This slanting face, by one-sided reaction with the sawdust, maintains the chain steadily pressed against one side of the groove, and thereby steadies the chain in the guide rail.

In Figs. 9 and 10, I have illustrated a simple and effective method for giving the cutting teeth an additional tip set for the purpose set forth, or to compensate for loss of set due to wear. The cutting teeth are each of them given a main clearance set in which the tooth is angularly ofiset away from the median plane of the chain and is also angularly disposed from front to rear with respect to said plane. This original main clearance set is clearly shown in Figs. 4 and 5. When the teeth are sharpened, as previously described, the total efiective set of the lateral pairs of cutting teeth is reduced, this by reason of the fact that the two teeth of the pair converge downwardly and rearwardly toward the median plane. This loss of total set may be compensated, so as to maintain the original set, by tip-setting the teeth, as at [4, by means of a suitably dimensioned setting rod I3, as illustrated.

I claim:

1. In a cutting chain comprising structurally similar cutting teeth and raker teeth not exceeding in height said cutting-teeth, said teeth being assembled in longitudinal repetitive groups individually substantially symmetrical with respect to the median plane of the chain, said cutting teeth having leading faces terminating in oppositely projecting cuttingpoints determining the width of a kerf intended to remain in a straight plane during progress of the cut; said cutting points having an additive asymmetry with re-, spect to the median plane of the chain for the purpose of counteracting a tendency of the chain to aberrate from the said intended straight plane of the kerf.

2. As a new article of manufacture, a pivotally articulated cutting chain having cutting teeth disposed relatively at opposite sides of a median plane between the side faces and including the normal longitudinal center line of the chain, and raker teeth disposed relatively between said cutting teeth, the cutting teeth on one side of said plane, at least in part, differing in height from and additively exhibiting a greater height than the cutting teeth on the other side, said cutting teeth having inclined upper edges which lie in parallel planes tangential to imaginary cylinders of equal diameter and coaxial with the proximate axis of articulation of the teeth.

3. As a new article of manufacture, a pivotally teeth being susceptible of sharpening by grinding said leading edges, and said pairs of cutting teeth being thus sharpened in a common plane forming an angle other than 90 with said median plane, the tooth at one side of said plane thereby exhibiting a greater height than, and correspondingly leading, the companion cutting tooth on the other side of said plane and said raker teeth being lower than the cutting teeth.

4. As a new article of manufacture, a cutting chain having cutting teeth and raker teeth in longitudinally interspersed series arrangement, all teeth having straight inclined upper edges located in parallel planes, said planes being tangential to imaginary cylinders coaxial with the proximate axis of articulation of the teeth and equal for each functionally related set of teeth which make up the chain, the leading faces of some at least, of said teeth being formed transversely in a plane inclined to the direction of movement of the chain and to a median plane between the side faces and including the normal longitudinal center line of the chain, so that additively .the side edges of the said faces of the teeth so formed, which, by reason of said inclination, lead the opposite side edges will lie predominantly-on one side of the chain.

5. As a new article of manufacture, a cutting chain in accordance with claim 1 having raker teeth with rearwardly inclined tops, said tooth being swaged at the forward end of said inclined top so as to increase the hook angle of the tooth at the tip.

6. As a new article of manufacture, a cutting chain in accordance with claim 1 having cutting teeth arranged in lateral pairs, the cutting tips of said teeth being oppositely set.

7. A cutting chain having at the back thereof a plurality of longitudinally spaced plate-like projections or tails adapted for engagement in a slotted guide rail, said tails having hooked leading edges for clearing the said slot of sawdust and for transporting and distributing lubricating oil in the slot, and said leading edges being formed transversely in substantially parallel planes inclined to the direction of movement of the chain and tending reactively to maintain the said tail-against one side of said slot.

8. A cutting chain having cutting teeth disposed on each side of a median plane, said teeth having inclined upper edges which lie in parallel planes tangential to imaginary cylinders of equal diameter and coaxial with the proximate axes of articulation of the teeth, said upper edges being inwardly beveled, said teeth having front cutting edges forming an angle of more than 45 with said tops, said frontsbeing beveled and sharpene to cutting edges, the angles of said bevels insaid teeth-fronts at one side of said plane bei g additively more acute than the bevel angles in the teeth-fronts at the other side.

9. A cutting chain having cutting and raker teeth each having a single point, the points of said raker teeth not exceeding in height the points-of said cutting teeth, the'teeth of each set being structurally similar and being disposed substantially symmetrically on both sides of the median plane of the chain, the points of the teeth on one side of said plane being higher in an additive sense than the points of the teeth on the opposite side.

10. A cutting chain having articulated links provided, respectively, with cutting and raker teeth having straight upper edges located in parallel planes, said planes being tangential to imaginary cylinders coaxial with the proximate axes of articulation of the teeth and equal for each functionally related set of teeth which make up the chain, the points of said raker teeth not exceeding in height the points of said cutting teeth, all teeth being longitudinally arranged some in and others on opposite sides of the median plane of the chain, the points 01' the teeth on one side of said plane being higher in an additive sense than the points of the teeth on the opposite side.

11. A cutting chain in accordance with claim 9 characterized by the fact that the tops of the cutting teeth converge both rearwardly and downwardly.

12. A cutting chain according to chain 1 wherein the difference in the distances of two corresponding opposite cutting points in each of said groups measured from a reference plane containing the axes of articulation oi the chain is produced by sharpening said leading faces at an angle other than 90 to said median plane.

13. A cutting chain according to claim 10 wherein at least some of the teeth have, in an additive asymmetrical sense, their points projecting higher and wider on one side of the median plane than on the other.

14. A cutting chain according to claim 10 wherein the teeth have, in an additive asymmetrical sense, their points projecting wider on one side of the median plane than on the other.'

ARTHUR N.BLUM. 

